Effects of injecting excess arginine on rat pancreas.

When male rats were given single i.p. injection of 500 mg of L-arginine/100 g body weight, the pancreatic acinar cells were destroyed selectively, without any morphological change of Langerhans' islets. As early as 24 hours after the injection, loss of basophilia, zymogen degranulation, and vacuolar and necrotic changes of the acinar cells were noted. After 3 days, fibroblastic activity and atrophy of pancreatic lobuli were evident. Early electron microscopic findings were changes of the endoplasmic reticulum, such as partial dilatation or vacuolation of the cisternae, usually with loss of ribosomes attached to the membrane. The effect of arginine excess may be ascribed to imbalance of amino acids and subsequent to decrease of protein synthesis in the acinar cells. In the course of this study, fat necrosis with marked infiltration of leucocytes was observed in adipose tissues in peripancreatic, epididymal, omental and retroperitoneal areas. This change correlated closely with the marked necrosis of the pancreas. An increase in the level of lipase in the blood was also demonstrated.